Variable frequency sound generator

Abstract

A low frequency sound generator is depicted in FIG. 1, having a resonator tube with an open end and a closed end, with a pulsing mechanism for admitting puffs of compressed gas into the closed end for purposes of producing sound waves out of the open end. The pulsing mechanism resides inside, and is movable along the axis of the resonator tube at the closed end, providing the means of closure for said resonator tube. The axial position of the pulsing mechanism is set through adjusting means, and determines the effective length of the resonator tube, thereby controlling the resonant frequency of the emitted sound.

I claim:  
     
         1 . In a sound generator, having a resonator tube with an open end and a closed end, with a pulsing mechanism on the closed end admitting puffs of compressed gas into the closed end of the resonator tube for purposes of producing sound waves out of the open end of the tube, said sound generator being capable of producing sound at frequencies determined by the length of the resonator tube, said frequencies being the fundamental tone where the wavelength is equal to four times the effective length of the resonator tube, and all harmonics, said pulsing mechanism residing inside the resonator tube or an extension of the resonator tube at the closed end, being movable along the axis of the resonator tube to change the effective length of the resonator tube thereby changing the sound frequencies at which resonance is produced, and providing the means of closure for the resonator tube through sealing means provided between the pulsing mechanism and the resonator tube to establish the closed end boundary of the resonator tube.  
     
     
         2 . A sound generator according to  claim 1  where adjusting means are provided for changing the location of the pulsing mechanism axially inside the resonator tube to change the effective length of the resonator tube and the corresponding resonant sound frequencies.  
     
     
         3 . A sound generator according to  claim 1  where the resonator tube or resonator tube extension acts as the compressed gas inlet for the pulsing mechanism, providing a stationary attachment point for the inlet compressed gas connection and a reservoir for containment of the compressed gas for admittance through the pulsing mechanism and into the resonator tube.  
     
     
         4 . A sound generator according to  claim 3  where a cylindrically shaped pulsing mechanism projects through a circular opening in the rear of the resonator tube, sealing means being provided between said pulsing mechanism and said resonator tube to prevent leakage of gas from the pulser to the surrounding atmosphere.  
     
     
         5 . A sound generator according to  claim 1  where inflatable seals provide sealing means that can have their active pressure changed during movement or stationary periods.  
     
     
         6 . A sound generator according to  claim 2  where threaded rods provide adjusting means for the effective length of the resonator tube that can be manually or automatically turned to change the axial position of the pulsing mechanism.  
     
     
         7 . A sound generator according to  claim 2  where hydraulically actuated cylinders provide adjusting means for the effective length of the resonator tube that can be adjusted manually or automatically.  
     
     
         8 . A sound generator according to  claim 1  where an electric motor driven rotor in a cylinder provides an opening and closing action for the pulsing mechanism, said motor being an ac motor driven by a variable frequency power supply turning said rotor that contains ports allowing compressed gas contained in a reservoir surrounding the cylinder to enter into the resonator tube through the cylinder in modulated puffs when said rotor ports align with ports in the cylinder.  
     
     
         9 . A sound generator according to  claim 8  where said motor speed is controlled by a digital automatic controller receiving sound pressure signals from the closed end of the resonator tube and adjusting the motor speed to attain resonance.  
     
     
         10 . A sound generator according to  claim 2  where the position of the pulsing mechanism is adjusted automatically by a digital controller to attain sound resonance in the resonator tube at the desired sound output frequency.  
     
     
         11 . A method of generating a sound field inside of an enclosure for the purpose of agitating gas molecules to create useful turbulence where: 
 (a) one or more sound generators are installed around or within the enclosure for introducing sound into the enclosure;    (b) pressure transducers are installed in various locations throughout the enclosure to provide active indication of the sound pressure levels in those locations;    (c) a digital controller is used to control the sound generators to attain a resonating sound field within the enclosure.    
     
     
         12 . The method of  claim 11  where the frequency of the introduced sound is controlled to produce desired sound pressure levels at specific locations within the enclosure with the least amount of input energy by monitoring the sound pressure levels inside the enclosure at different sound input frequencies and utilizing frequencies where resonance is attained within the enclosure.  
     
     
         13 . The method of  claim 11  where the controller regulates the flow rate of compressed gas to the sound generator(s), thereby controlling the amount of sound energy introduced into the enclosure.  
     
     
         14 . The method of  claim 11  where multiple sound generators are simultaneously operated at the same frequency, and the phase relationship between the sound output from the generators is controlled to achieve favorable sound pressures in desired locations.  
     
     
         15 . The method of  claim 14  where the sound generators use servomotors to achieve matching output frequencies and control the phase relationship.